Method for producing 1-octene

ABSTRACT

The invention relates to a process for preparing 1-octene by reacting 1,3-butadiene with a telogen of the formula H—X—Y—H, where X is O, N, S or P and Y is C, N or Si and X and Y bear, depending on their valence, further substituents, in the presence of a telomerization catalyst to form a telomer of the formula H 2 C═CH—CH 2 —CH 2 —CH 2 —CH═CH—CH 2 —X—Y—H, partially hydrogenating the telomer to form a 1-substituted 2-octene of the formula H 3 C—CH 2 —CH 2 —CH 2 —CH 2 —CH═CH—CH 2 —X—Y—H and dissociating the 1-substituted 2-octene to give 1-octene.

BACKGROUND OF THE INVENTION

The invention relates to a process for preparing 1-octene bytelomerization of 1,3-butadiene by means of a telogen in the presence ofa telomerization catalyst, partial hydrogenation of the telomer anddissociation of the hydrogenated intermediate.

DESCRIPTION OF THE BACKGROUND

1-Octene is used in large quantities in the production of variouschemical products. For example, surface-active substances, plasticizers,lubricants and polymers are produced from 1-octene. Another large fieldof application is its use as comonomer in polymers, especially inpolyethylene.

Virtually all processes which are at present utilized commercially forthe production of 1-octene are based on ethene as raw material. Etheneis oligomerized to give a range of α-olefins as main products. Withappropriate choice of catalyst and process conditions, the amount of1-octene in the product can be optimized and is then about 25%. Apartfrom these processes, by means of which most 1-octene is produced, theisolation of 1-octene from the product mixture from the Fischer-Tropschreaction has attained some importance.

Apart from ethene-based processes, processes which use 1,3-butadiene asraw material are also known from the literature. However, 1-octene isnot obtainable directly, for example by means of a dimerization, frombutadiene, but is obtained after a plurality of process steps. Thus, WO92/10450 describes a process in which 1,3-butadiene is reacted with,preferably, methanol or ethanol to form a 2,7-octadienyl ether which,after hydrogenation to the octyl ether, is dissociated to give 1-octene.An analogous route is employed in EP-A-0 440 995, but the reaction inthe first step is with a carboxylic acid. The processes both involve ananalogous first process step which is generally referred to astelomerization. In the telomerization, a telogen (in EP-A-0 440 995, thecarboxylic acid) is generally reacted with a taxogen (1,3-butadiene, 2equivalents) to form a telomer.

Examples of telomerization reactions are described in, inter alia, E. J.Smutny, J. Am. Chem. Soc. 1967, 89, 6793; S. Takahashi, T. Shibano, N.Hagihara, Tetrahedron Lett. 1967, 2451; EP-A-0 561 779, U.S. Pat. Nos.3,499,042, 3,530,187, GB 1 178 812, NL 6 816 008, GB 1 248 593, U.S.Pat. Nos. 3,670,029, 3,670,032, 3,769,352, 3,887,627, GB 1 354 507, DE20 40 708, U.S. Pat. Nos. 4,142,060, 4,146,738, 4,196,135, GB 1 535 718,U.S. Pat. No. 4,104,471, DE 21 61 750 and EP-A-0 218 100.

In the butadiene-based processes for preparing 1-octene, as described,for example, in WO 92/10450 or EP-A-0 440 995, the 1-octene is obtainedby dis-sociation of an n-octane substituted in the 1 position. Theselectivities in this step are often unsatisfactory. Thus, WO 92/10450reports the selectivity to octenes in the dissociation of1-methoxyoctane at a conversion of 80% as being 66%.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to discover a process bymeans of which 1-octene can be prepared from 1,3-butadiene but whichcircumvents the abovementioned dissociation step.

It has now been found that 1-octene can be prepared in high purity andgood yield by a process which is made up essentially of three steps.

The invention accordingly provides a process for preparing 1-octene by

-   1) reacting 1,3-butadiene with a telogen of the formula I,

-   -   where X is O, N, S or P and Y is C, N or Si and X and Y may,        depending on the valence of X and Y, bear further substituents,        in the presence of a telomerization catalyst to form a telomer        of the formula II

-   -   where X and Y are as defined above,

-   2) partially hydrogenating the compound of the formula II to form a    compound of the formula III,

-   3) obtaining 1-octene by dissociation of the compound of the formula    III.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the telomerization in step 1) of the process of the presentinvention, it is possible to use either pure 1,3-butadiene or mixturesin which 1,3-butadiene is present. As 1,3-butadiene-containing mixtures,preference is given to using mixtures of 1,3-butadiene with otherC₄-hydrocarbons. Such mixtures are obtained, for example, in crackingprocesses for the production of ethene in which refinery gases, naphtha,gas oil, LPG (liquefied petroleum gas), NGL (natural gas liquid), etc.,are reacted. The C₄ fractions obtained as by-product in these processescomprise variable amounts of 1,3-butadiene, depending on the crackingprocess. Typical 1,3-butadiene concentrations in the C₄ fractionobtained from a naphtha steam cracker are 20–70% of 1,3-butadiene.

The C₄ components n-butane, i-butane, 1-butene, cis-2-butene,trans-2-butene and i-butene which are likewise present in thesefractions do not interfere, or do not interfere significantly, in thereaction in the telomerization step. On the other hand, dienes havingcumulated double bonds (1,2-butadiene, allene, etc.) and alkynes, inparticular vinylacetylene, act as moderators in the telomerizationreaction. It is therefore advantageous to remove the C₄-alkynes and ifnecessary the 1,2-butadiene beforehand. This may, if possible, becarried out by physical methods such as distillation or extraction.Possible chemical routes are selective hydrogenation of the alkynes toalkenes or alkanes and reduction of the cumulated dienes to monoenes.Processes for such hydrogenations are described in the prior art, forexample in WO 98/12160, EP-A-0 273 900, DE-A-37 44 086 or U.S. Pat. No.4,704,492.

As telogens in step 1 of the process of the invention, it is possible touse all compounds which have the formula I. In the formula I, X is O, N,S or P and Y is C, N or Si, where X and Y may, depending on the valenceof X and Y, bear further substituents. Preferred substituents on X and Yare hydrogen, alkyl radicals having 1–50 carbon atoms, aryl radicalshaving 6–50 carbon atoms and/or heteroaryl radicals, where thesubstituents may be identical or different and may in turn besubstituted by the groups alkyl, aryl, —F, —Cl, —Br, —I, —CF₃, —OR,—COR, —CO₂R, —OCOR, —SR, —SO₂R, —SOR, —SO₃R, —SO₂NR₂, —NR₂, —N═CR₂, —NH₂where R=H or a substituted or unsubstituted, aliphatic or aromatichydrocarbon radical having from 1 to 25 carbon atoms. Preference isgiven to X being O or N and Y being C.

Specific examples of telogens of the formula I are

-   -   monoalcohols such as methanol, ethanol, n-propanol, isopropanol,        allyl alcohol, n-butanol, i-butanol, octanol, 2-ethylhexanol,        isononanol, benzyl alcohol, cyclohexanol, cyclopentanol or        2,7-octadien-1-ol,    -   dialcohols such as ethylene glycol, 1,2-propane-diol,        1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 2,3-butanediol        and 1,3-butanediol,    -   hydroxy compounds such as α-hydroxyacetic esters,    -   primary amines such as methylamine, ethylamine, propylamine,        butylamine, octylamine, 2,7-octadienylamine, dodecylamine,        ethylenediamine or hexamethylenediamine,    -   secondary amines such as dimethylamine, diethyl-amine,        N-methylaniline, bis(2,7-octadienyl)amine, dicyclohexylamine,        methylcyclohexylamine, pyrrolidine, piperidine, morpholine,        piperazine or hexamethylenimine.

Telogens which can themselves be obtained via a telomerization reactioncan be used directly or else can be formed in situ. Thus, for example,2,7-octadien-1-ol can be formed in situ from water and butadiene in thepresence of the telomerization catalyst, 2,7-octadienylamine can beformed from ammonia and 1,3-butadiene, etc.

Telogens which are particularly preferably used are methanol, ethanol,n-butanol, ethylene glycol, 1,3-propanediol, dimethylamine anddiethylamine. Very particular preference is given to using methanol.

To determine the ratio of telogen to 1,3-butadiene in the telomerizationreaction, the number of active hydrogen atoms in the telogen has to betaken into account. Thus, for example, methanol has one active hydrogenatom, ethylene glycol has two, methylamine has two, etc.

From 0.001 mol to 10 mol of 1,3-butadiene are used in the telomerizationreaction for every mole of active hydrogen atoms of the telogen whichcan react with the 1,3-butadiene. When the reaction is carried out usinga liquid phase, a ratio of from 0.1 mol to 2 mol of 1,3-butadiene permole of active hydrogen is preferred.

As telomerization catalysts, it is possible to use homogeneous,heterogeneous or immobilized catalysts or combinations thereof. Manycatalysts for this reaction are described in the literature (cf. A.Behr, “Homogeneous Transition Metal Catalysts”, Aspects of HomogeneousCatalysis, 1984, 5, 3–73). For example, transition metals of transitiongroup VIII of the Periodic Table of the Elements and their complexes areused successfully as catalysts.

For the purposes of the present invention, the use of nickel, rhodium,palladium and platinum catalysts is preferred. Particular preference isgiven to using palladium catalysts. It is possible to use eitherpalladium(0) or palladium(II) compounds in the telomerization step.Examples of suitable palladium compounds are palladium(II) chloride,palladium(II) bromide, palladium(II) acetate, palladium(II) formate,palladium(II) octanoate, palladium(II) carbonate, palladium(II) sulfate,palladium(II) nitrate, palladium(II) acetylacetonate, palladium(II)alkyl-sulfonate, Na₂PdCl₄, K₂PdCl₄, dichlorobis(benzonitrile)palladium,allylpalladium chloride, allylpalladium acetate, trisallylpalladium,1,5-cyclo-octadienepalladium(II) chloride,bis(triphenylphosphine)palladium(II) chloride,(1,2-bis(diphenylphosphino)ethane)palladium(II) chloride. When usingpalladium halides, an activator needs to be added to the reaction, sincefree halide ions inhibit the telomerization reaction. The use ofpalladium(II) salts having organic anions, e.g. palladium acetate orpalladium acetylacetonate, is therefore preferred. Examples ofpalladium(0) complexes include complexes of palladium with phosphorus,nitrogen or arsenic donor atoms, alkyne, alkene and diene complexes.Examples of phosphorus ligands are phosphines, phosphites, phosphonitesor phosphinites, and examples of nitrogen ligands are amines, nitritesand pyridines. Specific examples aretetrakis(triphenylphosphine)palladium(0),tris(dibenzylideneacetone)dipalladium(0) andbis(1,5-cyclooctadiene)palladium.

The amount of telomerization catalyst used depends on its activity. Inprinciple, any amount of catalyst which ensures a sufficient reactionrate can be used. In homogeneously catalyzed reactions in which startingmaterials, products and a transition metal catalyst are present insolution in a single phase, it is usual to use from 0.1 ppm to 50 000ppm of metal (based on the reaction mixture). When using palladiumcatalysts, preference is given to using from 1 ppm to 1 000 ppm,particularly preferably from 3 ppm to 100 ppm, of catalyst metal.

If the telomerization is carried out in multiphase systems (for exampleheterogeneously catalyzed or two liquid phases of which one comprisesthe catalyst), these concentration ranges can be different. When thetelomerization is carried out in a plurality of liquid phases, it isparticularly advantageous for catalyst and product to be present indifferent phases, since the catalyst can then easily be separated off bymeans of phase separation. Water often forms one of the liquid phases.However, for example, perfluorinated hydrocarbons, ionic liquids andsupercritical carbon dioxide are also used (on the subject of ionicliquids, see P. Wasserscheid, W. Keim, Angew. Chem., Int. Ed. 2000, 39,3772–3789). The telomerization of butadiene by means of water in ionicliquids is described by J. E. L. Dullius, P. A. Z. Suarez, S. Einloft,R. F. de Souza, J. Dupont, J. Fischer, A. D. Cian, Organometallics 1999,17, 997–1000. A review of water as carrier phase for the catalyst may befound, for example, in B. Cornils, W. A. Herrmann (Eds.) “Aqueous-PhaseOrganometallic Catalysis”, Wiley-VCH, Weinheim, New-York, Chichester,Brisbane, Singapore, Toronto, 1998. In processes using a plurality ofliquid phases, it is particularly advantageous to use a telogen which ispresent together with the catalyst in one phase while the products aremainly present in a second phase.

The telomerization catalysts can be introduced in active form into theprocess, but it is often simpler to use a precursor which forms thecatalytically active species under the reaction conditions.

The course of the telomerization reaction can generally be improvedconsiderably by addition of ligands to the reaction. It is thereforeadvantageous to carry out step 1 of the process of the invention in thepresence of ligands. Suitable ligands are in principle all those whichincrease the reaction rate, improve the selectivity of the formation ofcompound II, increase the working life of the catalyst, etc. Examples ofsuitable ligands are compounds containing one or more trivalentphosphorus, arsenic, antimony or nitrogen atoms.

Examples of phosphorus ligands are:

-   phosphines such as triphenylphoshine, tris(p-tolyl)phosphine,    tris(m-tolyl)phosphine, tris(o-tolyl)phosphine,    tris(p-methoxyphenyl)phosphine,    tris(p-di-methylaminophenyl)phosphine, tricyclohexylphosphine,    tricyclopentylphosphine, triethylphosphine,    tris-(1-naphthyl)phosphine, tribenzylphosphine,    tri-n-butyl-phosphine, tri-tert-butylphosphine,    tris(3-sulfonato-phenyl)phosphine (metal salt),    bis(3-sulfonatophenyl)-phenylphosphine (metal salt),    (3-sulfonatophenyl)di-phenylphosphine (metal salt);-   phosphites such as trimethyl phosphite, triethyl phosphite,    tri-n-propyl phosphite, tri-i-propyl phosphite, tri-n-butyl    phosphite, tri-i-butyl phosphite, tri-tert-butyl phosphite,    tris(2-ethylhexyl) phosphite, triphenyl phosphite,    tris(2,4-di-tert-butyl-phenyl) phosphite,    tris(2-tert-butyl-4-methoxyphenyl) phosphite,    tris(2-tert-butyl-4-methylphenyl) phosphite, tris(p-cresyl)    phosphite;-   phosphonites such as methyidiethoxyphosphine,    phenyl-dimethoxyphosphine, phenyldiphenoxyphosphine,    2-phenoxy-2H-dibenz[c,e][1,2]oxaphosphorin and its derivatives in    which all or some of the hydrogen atoms are replaced by alkyl and/or    aryl radicals or halogen atoms;-   phosphinites such as diphenyl(phenoxy)phosphine and its derivatives    in which all or some of the hydrogen atoms are replaced by alkyl    and/or aryl radicals or halogen atoms, diphenyl(methoxy)phosphine,    diphenyl(ethoxy)phosphine, etc.

For the purposes of the present invention, phosphonium salts can alsofunction as ligands. Examples of suitable phosphonium salts and theiruse in telomerization may be found in, inter alia, EP-A-0 296 550.

When using transition metal catalysts, the ratio of ligand to metal(mol/mol) is normally from 0.1/1 to 500/1, preferably from 0.5/1 to50/1, particularly preferably from 1/1 to 20/1. The ligand can be addedto the reaction as such, in dissolved form or in the form of metalcomplexes. Additional ligand can be added to the reaction at any pointin time and at any location in the reactor as such, as a solution or inthe form of a metal complex.

It is often advantageous to carry out the telomerization reaction in thepresence of bases. Examples of suitable bases are metal hydroxides, inparticular alkali metal hydroxides and alkaline earth metal hydroxides,metal carbonates and metal hydrogencarbonates, in particular alkalimetal and alkaline earth metal carbonates and alkali metal and alkalineearth metal hydrogen carbonates, hydroxides of quaternary ammonium orphosphonium ions, alkoxides, enolates, phenoxides, metal salts ofcarboxylic acids, metal amides such as sodium amide or lithiumdiethylamide, alkali metal borohydrides, alkali metal aluminum hydridesand organic nitrogen bases, in particular amines such as triethylamine,pyridine or trioctylamine. It is particularly advantageous to use metalsalts of the telogen, corresponding to the formula IV.

In this formula, M is a monovalent metal or a fraction depending on thestoichiometry of a polyvalent metal. X and Y are as defined above. M ispreferably an alkali metal, alkaline earth metal, boron or aluminum,particularly preferably lithium, sodium or potassium. Compounds of theformula IV can often be obtained easily from the reaction of the telogenof the formula I with the metal. This can also be carried out in situ.

The amount of base added to the telomerization reaction is stronglydependent on the type of base used. When using transition metalcatalysts, it is normal to use from 0 to 50 000 mol of base per mole oftransition metal, preferably from 0.5 to 5 000 mol, particularlypreferably from 0.5 to 500 mol, of base per mole of transition metal. Itis also possible to use a plurality of bases at once.

The addition of other auxiliaries can be advantageous for carrying outstep 1 of the process of the invention. For example, it may beadvantageous to use inhibitors which suppress the polymerization ofbutadiene. Such inhibitors are normally present in commercial(stabilized) pure 1,3-butadiene. An example of a standard stabilizer istert-butylcatechol.

Step 1 of the process of the invention can be carried out in the absenceof solvents or with addition of solvents. The solvent used should belargely inert. Preference is given to the addition of solvents whentelogens which are solid under the reaction conditions are used or inthe case of products which would be obtained as solids under thereaction conditions. Suitable solvents include aliphatic, cycloaliphaticand aromatic hydrocarbons, for example C₃–C₂₀-alkanes, mixtures of loweror higher alkanes (C₃–C₂₀), cyclohexane, cyclooctane, ethylcyclohexane,alkenes and polyenes, vinylcyclohexene, 1,3,7-octatriene,C₄-hydrocarbons from C₄ fractions from crackers, benzene, toluene andxylene; polar solvents such as tertiary and secondary alcohols, amidessuch as acetamide, dimethylacetamide and dimethylformamide, nitrilessuch as acetonitrile and benzonitrile, ketones such as acetone, methylisobutyl ketone and diethyl ketone and diethyl ketone, carboxylic esterssuch as ethyl acetate, ethers such as dipropyl ether, diethyl ether,methyl tert-butyl ether (MTBE), dimethyl ether, methyl octyl ether,3-methoxyoctane, dioxane, tetrahydrofuran, anisole, alkyl and arylethers of ethylene glycol, diethylene glycol and polyethylene glycol andother polar solvents such as sulfolane, dimethyl sulfoxide, ethylenecarbonate and propylene carbonate. Water can also be used as solvent.The solvents are used alone or as mixtures of various solvents.

Step 1 of the process of the present invention is advantageously carriedout in the absence of oxygen, since oxygen has an adverse effect on thestability of the catalyst systems.

The temperature at which the telomerization reaction is carried out isin the range from 10° C. to 200° C., preferably from 40° C. to 150° C.,particularly preferably from 40° C. to 110° C. The reaction pressure isfrom 1 bar to 300 bar, preferably from 1 bar to 120 bar, particularlypreferably from 1 bar to 64 bar and very particularly preferably from 1bar to 20 bar.

For the purposes of the process of the invention, it is not necessary toachieve complete conversion of the butadiene in the telomerization. Thebutadiene conversion is from 5% to 100%, preferably from 50% to 100%,particularly preferably from 80% to 100%.

Step 1 of the process of the invention can be carried out continuouslyor batchwise and is not restricted to the use of particular types ofreactor.

Examples of reactors in which the reaction can be carried out arestirred tank reactors, cascades of stirred tanks, flow tubes and loopreactors. Combinations of various reactors are also possible, forexample a stirred tank reactor together with a downstream flow tube.

The heat of reaction which is evolved in the reaction is removed byknown methods, for example by means of internal or external coolers.Specifically, this may involve the use of shell-and-tube reactors,reactors with cooling fingers, cooling coils or cooling plates or plantswhich involve cooling of a recycle stream (recirculation reactors,reactors with recycle).

The telomerization catalyst used in step 1 of the process of theinvention can be recovered after the telomerization reaction and all orsome of it can be used for further telomerization reactions (cf. EP-A-0218 100). The catalyst can be separated off by, for example,distillation, extraction, precipitation or adsorption. If all or some ofthe catalyst is present in a second phase, it can be separated offsimply by separation of the phases.

It is also possible for the catalyst to be modified prior to beingseparated off or during the separation. This applies analogously to thetotal or partial recirculation in the process, which can likewise bepreceded by modification of the catalyst. For example, U.S. Pat. No.4,146,738 describes a process in which the catalyst is stabilized bymeans of auxiliaries prior to being separated off. After separation fromthe other products, it is activated and returned to the process.

As an alternative, the catalyst can also be worked up in other waysafter the reaction (cf. WO 90/13531, U.S. Pat. No. 5,254,782).

If the telogen used is not reacted completely in step 1, the excesstelogen is preferably separated off from the output from step 1 of theprocess of the invention and all or some of it is returned to step 1.

Step 1 of the process of the invention results in formation of theproduct of the formula II together with, as by-products, mainly1,7-octadiene substituted in the 3 position, 1,3,7-octatriene and4-vinylcyclohexene. Small amounts of relatively high-boiling componentsare also present. For the further process, it can be advantageous toseparate off all or part of the by-product from the product of theformula II. In principle, all methods or combinations of methods bymeans of which the compound of the formula II can be separated from theproduct mixture can be employed. The preferred separation technique isdistillation. The distillation can be carried out using all availableapparatuses and techniques, for example tray columns, packed columns,dividing wall columns, extractive distillation, thin film evaporatorsand falling film evaporators. The separation by distillation can becarried out in one or more steps and is dependent on the boiling pointsof the components present in the product mixture. Ifbutadiene-containing mixtures of C₄-hydrocarbons are used as feedstocks,the remaining C₄-hydrocarbons have the lowest boiling point and cantherefore easily be separated off at the top of the distillationapparatus.

When isobutene is present in the remaining C₄-hydrocarbons and alcoholsare used as telogen, there is the additional possibility of separatingoff excess alcohol together with the C₄-hydrocarbons and reacting themfurther in other processes. For example, if isobutene is present in theC₄-hydrocarbons and methanol is used as telogen, then C₄-hydrocarbonsremaining after the telomerization can be separated off together withexcess methanol and fed together into an MTBE synthesis.

It can also be advantageous to isolate other components of the outputfrom step 1 of the process of the invention and, if appropriate, returnthem to the process or utilize them separately. As regards thetechniques used for this purpose, what has been said in the case of theisolation of the product of the formula II applies analogously.Components which may usefully be isolated are, in particular, thetelogen used, excess 1,3-butadiene, the 1,7-octadiene substituted in the3 position, 1,3,7-octatriene, 4-vinylcyclohexene, the base or bases usedand any solvent used.

The product of the formula II is hydrogenated in step 2 to form theproduct of the formula III. The product of the formula II can be usedhere in pure form or else in mixtures with one or more of the othercomponents from step 1.

The hydrogenation to form the product of the formula III can be carriedout as a liquid-phase or gas-phase hydrogenation or by a combination ofthese techniques and can be carried out in one or more steps, forexample in a preliminary hydrogenation and a final hydrogenation.

The hydrogenation can be carried out continuously or batchwise. Reactorsused can be the known standard reactors for hydrogenations, for exampletrickle bed reactors. The heat of reaction which is evolved in thereaction is removed by known methods, for example by means of internalor external coolers. Specifically, this may involve the use ofshell-and-tube reactors, reactors with cooling fingers, cooling coils orcooling plates or plants which involve cooling of a recycle stream(recirculation reactors, reactors with recycle).

The hydrogenation is carried out in the presence of a catalyst. It ispossible to use either homogeneous or heterogeneous catalysts. Forexample, transition metals, in particular copper, chromium and themetals of transition group VIII of the Periodic Table, are used ascatalysts for this hydrogenation.

When using homogeneous catalysts, additional ligands can be usedtogether with the catalyst metal. Examples of suitable ligands arecompounds of trivalent phosphorus (for example phosphines orphosphites), compounds of trivalent arsenic or antimony, nitrogencompounds (for example amines, pyridines, nitrites), halides, carbonmonoxide and cyanide.

In the case of heterogeneous catalysts, the abovementioned metals may bemodified with other metals or moderators. Thus, for example the activityand selectivity of heterogeneous palladium catalysts are frequentlymodified by addition of sulfur or carbon monoxide. A proportion ofchromium is frequently added to copper catalysts.

The use of supported catalysts is generally advantageous since smalleramounts of metal are required and the properties of the catalyst canadditionally be influenced via the nature of the support. Supportmaterials which have been found to be useful are, for example, activatedcarbon, aluminum oxide, silicon dioxide, silicon aluminum oxide, bariumcarbonate, barium sulfate and kieselguhr.

The hydrogenation of the 2,7-octadienyl radical to the 2-octenyl radicalis known from the literature. Examples of the homogeneously catalyzedhydrogenation may be found in Chemistry Letters 1977, 1083–1084 andBull. Chem. Soc. Jap. 1968, 41, 254–255. U.S. Pat. No. 5,118,837describes the use of heterogeneous catalysts.

The hydrogenations are carried out at temperatures of from 0 to 400° C.,preferably from 20 to 200° C. The pressure is in the range from 0.01 to300 bar, preferably from 0.1 to 125 bar, particularly preferably from 1to 64 bar.

The hydrogenation in the liquid phase, regardless of whether it ishomogeneously or heterogeneously catalyzed, can be carried out in theabsence of solvents or in the presence of additional solvents. Examplesof suitable solvents are aliphatic and cycloaliphatic hydrocarbons suchas C₃–C₁₆-alkanes, mixtures of lower or higher alkanes (C₃–C₂₀),cyclohexane, cyclooctane and ethylcyclohexane; alcohols such asmethanol, ethanol, propanol, isopropanol, n-butanol, isobutanol,2-ethylhexanol, isononanol and isotridecanol; polyols such as ethyleneglycol, propylene glycol, 1,3-propanediol and 1,4-butanediol; carboxylicesters such as ethyl acetate; ethers such as dipropyl ether, diethylether, dimethyl ether, methyl tert-butyl ether, methyl octyl ether,3-methoxyoctane, dioxane, tetrahydrofuran, alkyl ethers of ethyleneglycol, diethylene glycol and polyethylene glycol; sulfolane, dimethylsulfoxide, ethylene carbonate, propylene carbonate and water. Thesolvents are used alone or else as mixtures of various solvents.

When the hydrogenation is carried out in the liquid phase, a pluralityof liquid phases can be present. This method is particularlyadvantageous when catalyst and product are present in different phases,since the catalyst can then easily be separated off by phase separation.Water often also forms one of the liquid phases. However, for example,perfluorinated hydrocarbons, ionic liquids and supercritical carbondioxide are also used (on the subject of ionic liquids, see P.Wasserscheid, W. Keim, Angew. Chem., Int. Ed. 2000, 39, 3772–3789). Areview of water as carrier phase for the catalyst may be found, forexample, in B. Cornils, W. A. Herrmann (Eds.) “Aqueous-PhaseOrganometallic Catalysis”, Wiley-VCH, Weinheim, New York, Chichester,Brisbane, Singapore, Toronto, 1998.

In the case of hydrogenations in the gas phase, other gases may bepresent in addition to hydrogen and substrate. For example, nitrogenand/or argon and/or alkanes which are gaseous under the hydrogenationconditions, for example methane, propane or butane, can be added.

Both in gas-phase hydrogenations and in liquid-phase hydrogenations, oneor more components from step 1 of the process of the invention can bepresent in the full or in part. It is possible for these components alsoto be reduced under the conditions of the hydrogenation. Thus, forexample, the 1,7-octadienes substituted in the 3 position which areformed as by-product are at least partly hydrogenated, while the1,3,7-octatriene is likewise converted at least partly into lessunsaturated or saturated species (octadienes, octenes, octane).

The hydrogenation in step 2 of the process of the invention can becarried out continuously, semicontinuously or batchwise. It ispreferably carried out continuously.

In step 2 of the process of the invention, a very complete conversion ofthe compound of the formula II is preferably achieved. However, it isalso possible to stop the reaction at a partial conversion and toseparate off the unreacted compound II from the remaining components andreturn it to step 2 or, if desired, utilize it otherwise.

The product of the formula III from step 2 is converted in a third stepinto 1-octene and further dissociation products. It may be useful topurify the product of the formula III beforehand by physical methods. Inprinciple, it is possible to employ all methods or combinations ofmethods by means of which the by-products can be completely or partlyseparated off from the compound of the formula III. The preferredseparation technique is distillation. The distillation can be carriedout using all available apparatuses and techniques, for example traycolumns, packed columns, dividing wall columns, extractive distillation,thin film evaporators and falling film evaporators. The separation bydistillation can be carried out in one or more steps and is dependent onthe boiling points of the components present in the product mixture.

In step 3 of the process of the invention, the compound of the formulaIII is dissociated (cracked) to form 1-octene. The further dissociationproducts are dependent on the telogen used in step 1. For example, whenmethanol is used as telogen in step 1 of the process of the invention,formaldehyde is formed, while when ethanol is used, acetaldehyde isformed, when n-butanol is used, butanal is formed, and when diethylamineis used, ethylethylidenimine.

The dissociation can be carried out either in the liquid phase or in thegas phase. The dissociation can be carried out in the presence of anyamount of other substances which are inert or largely inert under thedissociation conditions. For example, nitrogen or argon or else water,water vapor or alkanes such as methane, propane or butane can be added.

The temperature at which the dissociation of the compound of the formulaIII is carried out is in the range from 100 to 800° C., preferably from150 to 600° C., particularly preferably from 250 to 500° C.

The pressure is from 0.05 to 300 bar, preferably from 1 to 125 bar,particularly preferably from 1 to 64 bar.

The dissociation reaction can be carried out in the absence of catalystsor in the presence of heterogeneous catalysts. Preference is given tousing catalysts which have Lewis-acid centers, for example amorphoussilica-aluminas, aluminas, silicas, silica gels, aluminum-containingsilica gels, clay minerals and zeolites.

The dissociation in step 3 of the process of the invention can becarried out continuously, semicontinuously or batchwise.

A further process variant is dissociation of the compound of the formulaIII with the dissociation products being separated off at the same time.The dissociation products can, for example, be separated off via the gasphase. This can, for example, be achieved technically by means of adistillation; in the lower, hotter part of the distillation, thecompound of the formula III is dissociated, while the 1-octene formedand, if appropriate, further dissociation products are separated off atthe top.

In the dissociation, all or part of the compound of the formula III isdissociated. In the case of partial conversion, the output from thedissociation still contains unreacted starting material of the formulaII. This can, after the 1-octene formed and, if appropriate, otherdissociation products have been separated off, be returned to thedissociation. However, it is also possible for only the 1-octene andpart of the other dissociation products to be separated off and therecycled stream to be recirculated to the prepurification upstream ofthe actual dissociation.

The 1-octene is separated from the other components of the output fromthe dissociation by known methods, for example phase separation,extraction, scrubbing, distillation or precipitation. It is stronglydependent on the telogen used in the telomerization. Thus, theformaldehyde formed in the dissociation of 1-methoxy-2-octene can beseparated from the 1-octene simply by extraction with water. If water orwater vapor is added in the dissociation of 1-methoxy-2-octene, anaqueous formaldehyde solution is formed in the work-up. In both cases,the organic phase comprising the 1-octene can then be further purified,for example by distillation. On the other hand, if butanol, for example,is used as telogen in the telomerization step, the dissociation of the1-butoxy-2-octene forms, inter alia, butyraldehyde. In this case, theproducts of the dissociation can be separated into the individualcomponents by, for example, distillation.

The dissociation of the compound of the formula III forms, in additionto 1-octene, other dissociation products containing unsaturated bonds(double and/or triple bonds) which in the present description arereferred to as dissociation products IV. One option according to thepresent invention is to hydrogenate these dissociation products by meansof hydrogen. This hydrogenation can be carried out directly during thedissociation, subsequent to the dissociation or after partial orcomplete separation of the products from step 3 of the process of theinvention. The product of the hydrogenation can, if desired afterpurification, be used in full or in part as telogen in step 1. Forexample, if ethanol is used as telogen, step 3 of the process of theinvention forms acetaldehyde which is converted by hydrogenation backinto ethanol, butanol correspondingly forms butyraldehyde which can behydrogenated to form butanol again, etc.

The hydrogenation of the dissociation product IV is carried out in oneor more stages in the presence of catalysts. The hydrogenation in theindividual stages can be carried out in the gas phase or in the liquidphase. It is possible to use homogeneously dissolved catalysts orheterogeneous catalysts. Preference is given to using heterogeneouscatalysts. For example, transition metals are used as catalysts for thehydrogenation of the dissociation product IV. Particular mention may bemade of copper, chromium and the metals of transition group VIII of thePeriodic Table.

In the case of heterogeneous catalysts, the abovementioned metals may bemodified with other metals or moderators. For example, a proportion ofchromium is often added to copper catalysts.

The use of supported catalysts is generally advantageous, since smalleramounts of metal are required and the properties of the catalyst canadditionally be influenced via the nature of the support. Supportmaterials which have been found to be useful are, for example; activatedcarbon, aluminum oxide, silicon dioxide, silicon aluminum oxide, bariumcarbonate, barium sulfate and/or kieselguhr.

The hydrogenations of the dissociation products IV are, if they are notcarried out under the conditions of the dissociation, carried out attemperatures of from 0 to 400° C., preferably from 50 to 250° C. Thepressure is in the range from 0.01 to 300 bar, preferably from 0.1 to125 bar, particularly preferably form 1 to 64 bar.

Reactors used can be the known standard reactors for hydrogenations, forexample trickle bed reactors. The heat of reaction which is evolved inthe reaction is removed by known methods, for example by means ofinternal or external coolers. Specifically, this may involve the use ofshell-and-tube reactors, reactors with cooling fingers, cooling coils orcooling plates or plants which involve cooling of a recycle stream(recirculation reactors, reactors with recycle).

If the dissociation of the compounds of the formula III and thehydrogenation of the dissociation products IV are carried out in asingle step, the heterogeneous catalysts described above for therespective reactions can be used side by side. It is also possible touse catalysts which catalyze both reactions, for example transitionmetals on Lewis-acid supports. In this case, the dissociation reactionhas to be carried out in the presence of hydrogen.

The hydrogenation in the liquid phase, regardless of whether it ishomogeneously or heterogeneously catalyzed, can be carried out in theabsence of solvents or in the presence of additional solvents. Examplesof suitable solvents are water, aliphatic and cycloaliphatichydrocarbons such as C₃–C₁₆-alkanes, mixtures of lower or higher alkanes(C₃–C₂₀), cyclohexane, cyclooctane and ethylcyclohexane; alcohols suchas methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol,2-ethylhexanol, isononanol and isotridecanol; polyols such as ethyleneglycol, propylene glycol, 1,3-propanediol and 1,4-butanediol; carboxylicesters such as ethyl acetate; ethers such as dipropyl ether, diethylether, dimethyl ether, methyl tert-butyl ether, methyl octyl ether,3-methoxyoctane, dioxane, tetrahydrofuran, alkyl ethers of ethyleneglycol, diethylene glycol and polyethylene glycol; sulfolane, dimethylsulfoxide, ethylene carbonate and propylene carbonate. The solvents areused alone or else as mixtures of various solvents.

In the dissociation, small amounts of other C₈-olefins can be formed inaddition to the 1-octene. Thus, 2-octene can be formed by isomerizationof 1-octene, 3-octene can be formed from the 2-octene, etc. Octane andoctadiene can also be formed. To achieve a very high 1-octene purity(>97%), it can therefore be necessary to separate off part of these C₈components. This can be carried out by distillation. This distillationcan either be carried out together with the separation of other productsfrom the dissociation step (and optionally the hydrogenation products ofthe dissociation products IV) or can be carried out separately as apurification of a previously isolated C₈ fraction.

The following examples illustrate the invention without restricting itsscope which is defined in the description and the claims.

EXAMPLES Example 1 Methanol as Telogen, 1-methoxy-2,7-octadiene

In a 70 l autoclave, 14 kg of methanol, 21 kg of 1,3-butadiene, 7.5 g ofpalladium(II) acetate, 85 g of triphenylphosphine and 160 g oftriethylamine were heated to 80° C. in the absence of water and oxygen.A pressure rise to 8 bar was observed. Under these conditions, thereaction started. The pressure decreased again with the commencement ofthe reaction of 1,3-butadiene. After 24 hours, the autoclave was cooledto room temperature and the remaining pressure was released. Accordingto GC analysis, 98% of the 1,3-butadiene had reacted. The main productsobtained were:

Component CAS No. Proportion in % Methanol 64-56-1 32.3 1,3,7-Octatriene1002-35-3 9.3 4-Vinylcyclohexene 100-40-3 0.2 3-Methoxy-1,7-octadiene20202-62-4 7.8 1-Methoxy-2,7-octadiene 14543-49-8 48.8 Others 1.6

To work up the output from the reactor, it was subjected to a batchdistillation at 80 mbar to separate it into a catalyst residue and adistillate.

Example 2 Homogeneously Catalyzed Hydrogenation

1000 g of 1-methoxy-2,7-octadiene, 500 ml of tetrahydrofuran, 500 ml ofethanol and 2.5 g of tris(triphenylphosphine)ruthenium(II) chloride wereplaced in a 3 l Büchi autoclave. The temperature was set to 30° C. andthe autoclave was pressurized to 30 bar by means of hydrogen. Thereaction was followed via the amount of hydrogen taken up and by meansof GC analyses. After 6 hours, the reaction was stopped. According to GCanalysis, 98% of the 1-methoxy-2,7-octadiene had reacted to form1-methoxy-2-octene (cis and trans) with a selectivity of 89%. The1-methoxy-2-octene was separated from solvents and catalyst bydistillation.

Example 3 Heterogeneously Catalyzed Hydrogenation

A gradient-free differential circulation reactor from Xytel was chargedwith 15 g of a heterogeneous ruthenium catalyst. To immobilize thecatalyst, it was located in a small wire mesh basket. The proportion byweight of ruthenium on the support material λ-Al₂O₃ was 1% by weight.Before commencement of the reaction, the catalyst was reduced in ahydrogen atmosphere at 200° C. After the reduction, 900 ml of a mixtureof trans-1-methoxy-2,7-octadiene and cis-1-methoxy-2,7-octadiene in amass ratio of 96:4 were introduced into the differential circulationreactor. The reaction mixture was hydrogenated under batch conditions ata hydrogen partial pressure of 10 bar. According to GC analysis, theprogress of the reaction at 40° C. was as follows:

LHSV⁻¹ cis-MOE trans-MOE cis-MODE trans-MODE Others kg h/ltr % by wt %by wt % by wt % by wt % by wt 0.0083 0.13 1.33 6.25 91.25 1.04 0.01670.13 1.99 6.16 09.33 1.38 0.0250 0.18 3.05 6.20 88.40 2.17 0.0333 0.234.11 6.01 87.97 1.68 0.0417 0.33 5.57 5.95 86.12 2.04 0.0500 0.40 6.805.77 85.04 1.99 0.0667 0.50 8.71 5.60 82.11 3.08 0.0833 0.64 11.17 5.4580.26 2.48 0.1083 0.81 13.87 5.24 77.39 2.69 0.1333 1.00 16.95 4.9774.02 3.05 0.1583 1.18 19.87 4.74 70.87 3.35 0.3750 2.98 52.01 2.2436.08 6.69 0.4000 3.26 57.11 1.86 30.09 7.69 0.4250 3.48 61.01 1.5925.52 8.40 0.4500 3.67 65.01 1.28 21.55 8.49 0.4917 4.03 73.13 0.8013.47 9.58 0.5250 4.20 76.2 0.54 8.67 10.39 (cis-MOE =cis-1-methoxy-2-octene, trans-MOE = trans-1-methoxy-2-octene, cis-MODE =cis-1-methoxy-2,7-octadiene, trans-MODE = trans-1-methoxy-2,7-octadiene)

The above-described trial was repeated at 50° C. under otherwiseidentical experimental conditions. As expected, the reaction rateincreased with temperature. According to GC analysis, the progress ofthe reaction at 50° C. was as follows:

LHSV⁻¹ cis-MOE trans-MOE cis-MODE trans-MODE Others kg h/ltr % by wt %by wt % by wt % by wt % by wt 0.0083 0.12 2.77 3.80 90.33 2.99 0.01670.16 4.16 3.77 89.14 2.76 0.0250 0.23 6.01 3.71 87.20 2.85 0.0333 0.317.83 3.64 84.24 3.98 0.0417 .036 9.01 3.63 83.13 3.87 0.0583 0.48 11.843.55 79.63 4.50 0.0917 0.70 17.08 3.31 73.20 5.70 0.1167 0.88 21.37 3.1668.21 6.38 0.3667 3.06 64.30 1.09 17.87 13.68 0.3833 3.28 67.72 0.8813.97 14.15 0.4000 3.44 70.27 0.72 10.82 14.75 0.4167 3.59 71.53 0.718.01 16.16 0.4333 1.28 74.29 0.44 5.52 18.48 0.4667 3.91 75.77 0.30 1.5118.51

Example 4 Dissociation to Give 1-octene

A gaseous mixture of 1-methoxy-2-octene (cis and trans) [CAS 60171-33-7]and nitrogen was fed continuously into a 100 ml gradient-freedifferential circulation reactor. The total amount fed in was 60standard ml/min. The proportion of inert gas in the feed was 83%. Thedissociation of 1-methoxy-2-octene into 1-octene and formaldehyde wascarried out under atmospheric pressure in a temperature range of375–450° C. Based on the 1-methoxy-2-octene in the feed gas, thefollowing conversions of 1-methoxy-2-octene and selectivities to1-octene were observed at a residence time of 40 s:

Temperature [° C.] 375 400 425 Conversion of methyl 2-octenyl ether [%]4.83 16.7 36.7 Selectivity of formation of 1-octene [%] 89.7 77.7 75.7

1. A process for preparing 1-octene, which comprises: (I) reacting1,3-butadiene with a telogen of the formula H—X—Y—H, where X is O, N, Sor P and Y is C, N, or Si and X and Y bear, depending on their valence,further substituents, in the presence of a telomerization catalyst toform a telomer of the formula:H₂C═CH—CH₂—CH₂—CH₂—CH═CH—CH₂—X—Y—H  (II), (II) hydrogenating thetelomere to form a 1-substituted 2-octene of the formula:H₃C—CH₂—CH₂—CH₂—CH₂—CH═CH—CH₂—X—Y—H  (III); and (III) dissociating the1-substituted 2-octene to give 1-octene and other dissociation products(IV).
 2. The process for preparing 1-octene as claimed in claim 1,wherein the substituents on X and/or Y are hydrogen, alkyl radicalshaving 1–50 carbon atoms, aryl radicals having 6–50 carbon atoms and/orheteroaryl radicals, where the substituents are identical or differentand may in turn be substituted by the groups alkyl, aryl, —F, —Cl, —Br,—I, —CF₃, —OR, —COR, —CO₂R, —OCOR, —SR, —SO₂R, —SOR, —SO₃R, —SO₂NR₂,—NR₂, —N═R₂, —NH₂ where R=H or a substituted or unsubstituted, aliphaticor aromatic hydrocarbon radical having from 1 to 25 carbon atoms.
 3. Theprocess for preparing 1-octene as claimed in claim 1, wherein thetelogen comprises a compound selected from the group consisting of amonoalcohol, a dialcohol, a primary amine and a secondary amine.
 4. Theprocess for preparing 1-octene as claimed in claim 3, wherein thetelogen comprises a compound selected from the group consisting ofmethanol, ethanol, n-propanol, isopropanol, allyl alcohol, n-butanol,i-butanol, octanol, 2-ethylhexanol, isononanol, benzyl alcohol,cyclohexanol, cyclopentanol, 2,7-octadien-1-ol, ethylene glycol,1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol,2,3-butanediol, 1,3-butanediol and an α-hydroxyacetic ester.
 5. Theprocess for preparing 1-octene as claimed in claim 3, wherein thetelogen comprises a compound selected from the group consisting ofmethylamine, ethylamine, propylamine, butylamine, octylamine,2,7-octadienylamine, dodecylamine, ethylenediamine,hexamethylenediamine, dimethylamine, diethylamine, N-methylaniline,bis(2,7-octadienyl)amine, dicyclohexylamine, methylcyclohexylamine,pyrrolidine, piperidine, morpholine, piperazine and hexamethylenimine.6. The process for preparing 1-octene as claimed in claim 1, whereinfrom 0.001 mol to 10 mol of 1,3-butadiene is reacted in step (I) forevery mole of active hydrogen atom reacted in said hydrogenation step.7. The process for preparing 1-octene as claimed in claim 1, whereintelogen which has not reacted in step (I) is recovered and returned tostep (I).
 8. The process for preparing 1-octene as claimed in claim 1,wherein telomerization catalyst of step (I) comprises a transition metalof transition group VIII of the Periodic Table.
 9. The process forpreparing 1-octene as claimed in claim 8, wherein the transition metalis palladium.
 10. The process for preparing 1-octene as claimed in claim1, wherein telomerization catalyst comprises a catalyst metal and aligand, and the ligand is a compound comprising a trivalent phosphorus,arsenic, antimony or nitrogen atom.
 11. The process for preparing1-octene as claimed in claim 10, wherein the ligand comprises a compoundselected from the group consisting of a phosphine, phosphite,phosphonite and a phosphinite.
 12. The process for preparing 1-octene asclaimed in claim 10, further comprising adding a base in step (I). 13.The process for preparing 1-octene as claimed in claim 1, wherein thetelomerization catalyst of step (I) is recovered and returned in full orin part to the process.
 14. The process for preparing 1-octene asclaimed in claim 1, wherein the telomerization catalyst of step (I) isnot returned to step (I).
 15. The process for preparing 1-octene asclaimed in claim 1, wherein said hydrogenation is carried out in thepresence of hydrogen and a homogeneous hydrogenation catalyst in step(II).
 16. The process for preparing 1-octene as claimed in claim 1,wherein said hydrogenation is carried out in the presence of hydrogenand a heterogeneous hydrogenation catalyst in step (II).
 17. The processfor preparing 1-octene as claimed in claim 15, wherein the hydrogenationcatalyst comprises copper, chromium and/or a transition metal oftransition group VIII of the Periodic Table in step (II).
 18. Theprocess for preparing 1-octene as claimed in claim 1, wherein1,3,7-octatriene is formed as by-product in step (I) and all or part ofthe 1,3,7-octatriene is hydrogenated in step (II).
 19. The process forpreparing 1-octene as claimed in claim 1, wherein 1,3,7-octatrienesubstituted in the 3 position obtained as a by-product in step (I) andall or part of the 1,3,7-octatriene substituted in the 3 position ishydrogenated in step (II).
 20. The process for preparing 1-octene asclaimed in claim 1, wherein the dissociation in step (III) is carriedout at temperatures in the range from 150° C. to 600° C.
 21. The processfor preparing 1-octene as claimed in claim 1, wherein less than 5% ofC₈-hydrocarbons are present in the feed to the dissociation in step(III).
 22. The process for preparing 1-octene as claimed in claim 1,wherein the 2-octene substituted in the 1-position is only partlyconverted in step (III).
 23. The process for preparing 1-octene asclaimed in claim 1, wherein the unreacted 2-octene substituted in the1-position separated off from the remaining components of the outputfrom step (III) and is recirculated in full or in part to step (III).24. The process for preparing 1-octene as claimed in claim 1, whereinthe 2-octene substituted in the 1-position is recirculated to apurification step which precedes step (II).
 25. The process forpreparing 1-octene as claimed in claim 1, wherein, in step (III), thedissociation to give 1-octene is carried out simultaneously withseparation of the 1-octene and the products of dissociation formed fromstarting materials.
 26. The process for preparing 1-octene as claimed inclaim 1, wherein the dissociation in step (III) is carried out in thepresence of water or water vapor.
 27. The process for preparing 1-octeneas claimed in claim 1, wherein the dissociation in step (III) is carriedout in the presence of catalysts.
 28. The process for preparing 1-octeneas claimed in claim 16, wherein the hydrogenation catalyst comprisescopper, chromium and/or a transition metal of transition group VIII ofthe Periodic Table in step (II).
 29. The process for preparing 1-octeneas claimed in claim 1, wherein the products of dissociation (IV) otherthan 1-octene are hydrogenated by hydrogen during dissociation step(III).
 30. The process for preparing 1-octene as claimed in claim 1,wherein the products of dissociation (IV) other than 1-octene arehydrogenated by hydrogen subsequent to dissociation step (III).
 31. Theprocess for preparing 1-octene as claimed in claim 1, wherein theproducts of dissociation (IV) other than 1-octene are hydrogenated byhydrogen after partial or complete separation of the products ofdissociation from step (III).